Articles » PLX Devices Wideband O2 Install

3. Now that you have your boxes mounted and your ready to go, it's time to ground them out. I ran all my ground wires from all 3 devices to the same point. There is a little hole in the metal frame behind the cup holder mounting position. I crimped all 3 wires into a holder and then used a small bolt and lock washers to secure it to the frame.

4. Now you can connect your power wires. You need a 12v KEYED supply. Meaning it's only on when you turn the key on. Now since I mounted mine where I did, I looked up and found my A/C controls power supply cable. It's a large blue\ blk stripped wire that runs up to the A/C controls right there in the center of the car. There is a Junction Connector that it passes through, and you can just tap it off from either side of this. I used this, for 2 reasons. It’s a large wire that I know is producing a very stable and reliable 12v signal, and I have no A/C, so I will not be drawing power from this for any other reason. If you have A/c, I would recommend using the noise filtering capacitors that they include in the kit for your power wires, just to be safe that you are still getting a good 12V signals with no electrical noise. After all, this is a wideband O2; you want it to be a clean, clean signal.


5. Once you have ground and power, let's move onto the signal wires. Now I ran the White wire from the PLX Autometer converter device, your wideband output signal (0V - 5V), over to the actual O2 controller box, cut the one short coming out of the controller, and soldered the 2 connections together. No worries on matching colors. White to white.

6. Once you have that all taken car of, now it's time to move to the Purple and Violet wires coming off your A/F gauge and the Converter box. These 2 should be cut fairly short, and then soldered together. The box and the A/F gauge are fairly close together, so there was no routing of any cables or anything difficult about this.

7. Okay. So now it's time to tap that new low voltage narrowband (Grey wire from PLX controller box) to your ECU. Unplug the ECU and locate the 16P connector. Connector D in the Helms manual. Locate the large white wire going into pin 7 on the clip.
With the clip on top, and looking at it from the wire side of the terminal, it is the wire that is on the 2nd row, 2nd wire over. It is a fairly large White wire, and if I remember correctly, the only white wire going into the connector.

***NOTE***
I have a 98 Ex, and I used the Helms for a Si. There was nothing in it to state that this wire was the same between the 2 models, but I checked continuity between the stock harness and the plug to make sure this was correct. It is. It should be the same from all 6th gen Civics at the minimum.

Cut this wire, but please remember to leave yourself something to tap back into in case you ever remove this wideband O2. Meaning, don't cut the wire off right at the plug. A good rule of thumb I play by, leave at least 3 inches behind to re-tap later if needed.
Now I also have an OBD-II to OBD-I converter harness, so I just cut this instead of my stock harness. But remember, to locate the correct wire on the harness still. ;)
Solder this connection and your done.

8. Now it's time to get dirty. Crawl under your car and remove your stock O2 sensor. Then install the new Bosch LSU4.2 Wideband sensor.

9. Route your cables however you would like. Connect the wire harness provided by PLX to the O2 Sensor and then route it through he firewall.
I used a slightly diff method. The wire coming off the sensor is quite long. So I ran it up and over the rear cross member, reached up from near my cat and grabbed a hold of it. I used a few tie wraps here and there to make sure it was secure and not bouncing al around. I also made sure the connector was physically behind shit so that water and dirt cannot get to it as easily as in the open space down there. I then ran the O2 wire harness into the cabin of the car using the OLD secondary O2 sensor hole above the cat. Being OBD-I now, I only have a primary after all. This was a good chance for me to get rid of the jumper harness that Honda has in there for connecting the Secondary O2. Now this exit hole is right under the carpet near the heater vents in the center console area under the dash. Perfect spot, considering my Controller box is mounted right there. :)
Connect your connector from the Controller box and this harness together and your done.